EPSC Abstracts
Vol. 5, EPSC2010-463, 2010
European Planetary Science Congress 2010
c Author(s) 2010
The Gulliver Mission: Sample Return from Deimos
D. Britt
University of Central Florida, 4000 Central Florida Blvd., Orlando FL 32816 ([email protected])
Abstract
The Gulliver Mission is designed to collect a
kilogram of Deimos regolith and return it to Earth.
Deimos is an attractive sample return target because:
(1) Its spectral D-type material is probably primitive
carbonaceous material that is poorly represented in
the meteorite collection; (2) Deimos one of the
smoothest small bodies know making it much easier
to find a safe sampling site; (3) Deimos is much
small and farther from Mars making proximity
maneuvering and orbital determination much easier
than at Phobos; (4) Deimos is high in the Martian
gravity well reducing the energy requirements for
rendezvous and return.
1. Introduction
The Martian moon Deimos presents a unique
opportunity for a sample return mission. Deimos is
spectrally analogous to type D asteroids, which are
thought to be composed of highly primitive
carbonaceous material that originated in the outer
asteroid belt. It also is in orbit around Mars and has
been accumulating material ejected from the Martian
surface ever since the earliest periods of Martian
history, over 4.4 Gyrs ago [1].
Deimos’s position in the Martian gravity well makes
it likely to accumulate and retain material. Much of
the ejecta from Deimos will not have the velocity to
escape the Martian system and will eventually
reaccrete to the moon [2]. Deimos is also probably a
low-density rubble-pile and that structure strongly
dissipates impact energy, further limiting ejection
velocities and material escape [3]. Because of
stochastic processes of regolith mixing over 4.4 Gyrs,
the rock fragments, grains, and pebble-sized
materials will likely sample the diversity of the
Martian ancient surface and as well as thoroughly
mixing the original primitive material of Deimos.
Modeling suggests that between 1-10% of the surface
material could be Martian ejecta.
Figure 1: The Martian moon Deimos
2. Gulliver Mission Plan
The Gulliver Mission has been proposed as a
Discovery/Mars Scout Class probe to directly collect
a kilogram of Deimos regolith and return it to Earth.
The spacecraft instrument suite is tightly focused to
the requirements of finding a safe and scientifically
interesting sampling location, collecting a sample,
and returning to Earth safely. They include a highresolution imaging camera for navigation and
sampling site selection, a radar altimeter for closedloop approach manoeuvring, and a wide-angle
descent imager to record the sampling site and the
actual sampling process.
Deimos is also by far the safest small body for
sample return yet imaged. Shown in Figure 2 is a
comparison of the surfaces of Deimos and 433 Eros.
The NEAR-Shoemaker mission succeeded in landing
on Eros with a spacecraft not designed for landing
and proximity manoeuvring. As can be seen in
Figure 2, Deimos is significantly less rough at 5-10
meter scales than Eros.
Compared to Phobos, Deimos has a number of
advantages as a sample return target. Phobos is
significantly rougher surface than Deimos with an
order of magnitude more blocks, much higher local
slopes, numerous impact and fracture scars.
Operationally, Phobos will be much harder to find a
safe, level sampling site. Higher local gravity and a
much greater tidal acceleration from Mars
complicates proximity operations and orbital
maneuvers. These challenges imply larger fuel
requirements for orbit and sampling at Phobos. In
addition Phobos is much farther inside the Mars
gravity well: The trip down to Phobos adds an
additional 440 m/s to ΔV requirements compared to a
mission to Deimos.
Figure 2: A comparison of the surface roughness of
Deimos and 433 Eros.
The
inherent
robustness
of
Earth-based
cosmochemical laboratory analysis, along with the
diversity of the sample, allows the mission scientific
goals to be both ambitious and comprehensive: (1)
Determine the geochemistry of the accretion zones
for the primitive D-type asteroids found in the outer
asteroid belt and near Jupiter. (2) Study pre-biotic
materials in primitive asteroids for their implications
on the chemistry and astrobiology of outer solar
system objects. (3) Determine the composition,
diversity, and crystallization history of the Martian
crust. (4) Date and characterize the era of Martian
heavy bombardment After initial processing these
samples will be made available as soon as possible to
the international cosmochemistry community for
detailed analysis.
References
[1] Burns, J. Contradictory clues as to the origin of the
Martian moons. In Mars (H. H. Kieffer, C. W. Snyder, and
M. S. Mathews Eds.), pp 1283-1301. Univ. Arizona Press,
Tucson, 1992.
[2] Hamilton, D. The asymmetric time variable rings of
mars. Icarus 119, 153-172. 1996.
[3] Housen K. R. The short-term evolution of orbital debris
coulds. J. of Astro. Sci. 40, 203-213. 1992.